JP2006342138A - Niobium 2-ethylhexanoate derivative and its preparation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a niobium 2-ethylhexanoate derivative useful as a precursor for an MOD (Metal Organic Deposition) method; and its preparation method. <P>SOLUTION: The niobium 2-ethylhexanoate derivative has a niobium content of 13-16 mass% and a carbon content of 50-58 mass%, consists only of niobium atoms, oxygen atoms, and 2-ethylhexanoic acid residues, and can be prepared by reacting pentakis(alkoxy)niobium with 2-ethylhexanoic acid. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a niobium 2-ethylhexanoate derivative having a specific structure and a method for producing the same.

  A ceramic thin film containing a niobium element has specific electrical characteristics, and therefore, its application to various uses is being studied. In particular, it is used for electronic members of electronic parts such as high dielectric capacitors, ferroelectric capacitors, gate insulating films, barrier films, piezoelectric elements, etc., which have applied the characteristics of excellent dielectric properties. For example, Non-Patent Document 1 reports a niobium-doped lead zirconate titanate (PNZT) thin film in which a portion of the titanium site of lead zirconate titanate is replaced with niobium.

  Examples of the method for producing the thin film include a MOD (Metal Organic Deposition) method such as a coating pyrolysis method and a sol-gel method, a CVD (Chemical Vapor Deposition) method, an ALD (Atomic Layer Deposition) method, and the like. For a thin film with relatively low processing accuracy, the MOD method is preferable because the manufacturing cost is low and the thin film can be easily formed. Thin film precursors used in the MOD method mainly use an alkoxide compound and an organic acid metal salt, and the same applies to niobium precursors.

  In Patent Document 1, the metal composition ratio (molar ratio) in the solution is represented by A: B: C = X: Y: Z (where A is Sr and Ba and / or Pb, B is Bi, C represents Ta and / or Nb), 0.4 ≦ X ≦ 1.0, 1.5 ≦ Y ≦ 3.5, Z = 2, and Sr: Ba: Pb = a: b: c. A composition for forming a Bi-based ferroelectric thin film obtained by mixing a metal compound in an organic solvent such that 0.7X ≦ a <X and 0 <b + c ≦ 0.3X when expressed (Claim 1) Is disclosed. [0023] In paragraph [0023] of Patent Document 1, as a niobium compound, an alkoxide such as niobium ethoxide, niobium propoxide, niobium butoxide, niobium-2-methoxyethoxide, niobium octylate, niobium n-hexanoate, Examples include carboxylic acids such as niobium 2-ethylbutyrate and niobium i-valerate.

Furthermore, Patent Document 2 discloses an underlayer having a composition of Bi ₂ (Ta _m Nb _1-m ) ₂ O ₈ (where 0 ≦ m ≦ 1) and a thickness of 5 to 50 nm, and the underlayer formed thereon, composition _{(Sr x Bi 1-x)} Bi 2 (Ta Y Nb 1-Y) 2 O z ( however, 0.4 ≦ X ≦ 1,0 ≦ Y ≦ 1, Z is the metal Bi-based ferroelectric thin film (Claim 1) and a composition of Bi ₂ (Ta _m Nb _1-m ) ₂ O ₈ (wherein the total number of oxygen associated with the element) , 0 ≦ m ≦ 1), and an underlayer having a thickness of 5 to 50 nm and a composition formed on the underlayer [{Sr _x (Pb and / or Ba _n } _X Bi _1-X) ] Bi ₂ (Ta _Y Nb _1-Y ) ₂ O _z (where 0 <n ≦ 0.3, 0.4 ≦ X ≦ 1, 0 ≦ Y ≦ 1, Z is associated with each metal element) A Bi-based ferroelectric thin film (Claim 2) comprising a main layer represented by the sum of the number of oxygen is disclosed in paragraph [0025] of Patent Document 2 as a niobium compound. , Alkoxides such as niobium ethoxide, niobium propoxide, niobium butoxide, niobium-2-methoxyethoxide and the like, and carboxylates such as niobium octylate, niobium n-hexanoate, niobium 2-ethylbutyrate, niobium valerate, etc. Is illustrated.

  Patent Document 3 discloses an electronic device including a step of providing a plurality of polyoxyalchelated metal moieties including perovskite type A-cytomoy, perovskite type B-cytomoy, and superlattice generating moiety. Combining each metal moiety in a relative proportion corresponding to a laminated superlattice material (112) having a plurality of layers (116, 124, 128) in sequence. Wherein the order comprises an A / B ionic subunit cell (146) formed from an oxide of a metal selected from the group consisting of A-site metal, B-site metal, and mixtures thereof. / B (124); superlattice-forming layer (116) with superlattice-forming ionic subunit cells; A-site metal and B- A perovskite type AB layer (128) containing both of theite metal, the AB layer comprising a perovskite type AB layer having a perovskite type oxygen octahedral lattice different from the lattice of the A / B layer. A step of applying the precursor solution to the substrate; and mixing the A / B layer, the superlattice generation layer, and the perovskite-type AB layer by treating the precursor solution on the substrate. Forming a laminated grid material is disclosed. Further, in Example 4 on page 47 of Patent Document 3, it is described that niobium 2-ethylhexanoate is used as a raw material for the pre-precursor solution.

Japanese Patent Laid-Open No. 9-25124 Patent Claims [0023] JP 9-142845 A Claims [0025] Japanese National Patent Publication No. 11-209683 Claim 47 Jpn. Appl. Phys. , Vol. 44, no. 1A (2005) pp. 267-274

  The organic acid niobium as described above has a problem that it is difficult to handle as a precursor of the MOD method because the properties and physical properties of the obtained derivative vary greatly depending on the production method and production conditions.

In general, niobium organic acid is often expressed as (RCOO) ₅ Nb, but there are various carbon contents and Nb contents. Actually, the binding unit forming the niobium organic acid is “RCOO-Nb and Nb—O—Nb”, “RCOO-Nb and Nb═O” or “RCOO-Nb and Nb—O—Nb and Nb═O”. For example, a model represented by a simple structure is represented by the following chemical formula, but it is difficult to accurately identify the chemical structure in practice. In the following chemical formula, L represents an organic acid residue.

Here, for example, an organic acid niobium derivative having a carbon content and Nb content close to the composition of (RCOO) ₅ Nb obtained by reacting niobium pentaalkoxide and an organic acid has poor storage stability. In addition, it is known that an organic acid niobium derivative obtained from niobium pentaalkoxide has an alkoxy group remaining easily. Actually, RCOO-Nb, Nb-O-Nb, Nb-OR '(OR' is It is considered to be a compound composed of a raw material-derived alkoxy group). In addition, the storage stability of the compound itself having the structure of (RCOO) ₅ Nb may be poor. On the other hand, when the Nb—O—Nb chain in the molecule is large, the molecular weight and niobium content increase, and the carbon content decreases. Since such organic acid niobium derivatives have poor solubility, the solvent that can be used and its concentration are limited, that is, the margin of solubility is narrowed. In addition, when used in combination with other metal precursors, niobium oxide is localized in the obtained thin film, so that there are many portions where the desired uniform composition and crystal structure cannot be formed. Characteristics are not obtained.

Furthermore, niobium 2-ethylhexanoate close to the theoretical value of Nb [C ₄ H ₉ CH (C ₂ H ₅ ) COO] ₅ , that is, a coating using a niobium content of about 11.5% by mass as a precursor. The liquid has a problem of poor storage stability. Further, such an organic acid niobium also has problems such as gelation or precipitation of the coating liquid due to a chemical reaction when used in combination with another precursor compound.

  Accordingly, an object of the present invention is to provide a niobium 2-ethylhexanoate derivative useful as a precursor for the MOD method and a method for producing the same.

As a result of intensive studies, the present inventors have found that a niobium 2-ethylhexanoate derivative having a specific structure can solve the above problems, and have completed the present invention.
That is, the niobium 2-ethylhexanoate derivative of the present invention has a niobium content of 13 to 16% by mass, a carbon content of 50 to 58% by mass, a niobium atom, an oxygen atom, and 2- It consists of only ethylhexanoic acid residues.

  The 2-ethylhexanoic acid niobium derivative can be produced by reacting pentakis (alkoxy) niobium with 2-ethylhexanoic acid.

  According to the present invention, it is possible to obtain a niobium 2-ethylhexanoate derivative suitable as a precursor for the MOD method, which is excellent in solubility in an organic solvent and can provide a stable solution when mixed with another precursor compound. It plays.

  The niobium 2-ethylhexanoate derivative of the present invention has a niobium content of 13 to 16% by mass, preferably 13 to 15% by mass, and a carbon content of 50 to 58% by mass, preferably 52 to 57%. It exists in the range of the mass%, and is comprised only from the niobium atom, the oxygen atom, and 2-ethylhexanoic acid residue. The theoretical value of niobium 2-ethylhexanoate has a niobium content of 11.5% by mass and a carbon content of 59.4% by mass.

  Here, when the niobium content is less than 13% by mass, the storage stability is deteriorated, which is not preferable, and when it exceeds 16% by mass, the solubility margin is not preferable. Further, if the carbon content is less than 50% by mass, the solubility margin becomes narrow, which is not preferable, and if it exceeds 58% by mass, the storage stability is deteriorated, which is not preferable.

  The features of the niobium 2-ethylhexanoate derivative of the present invention are liquid, excellent storage stability, excellent mixing stability, and a wide solubility margin. Therefore, a precursor for the MOD method is used. Useful as. Such characteristics also contribute to the selection of 2-ethylhexanoic acid as the organic acid component.

  For example, organic acid niobium derivatives having a small number of carbon atoms, which are organic acid components such as acetic acid and valeric acid, tend to be solidified and are difficult to give a stable coating solution. Moreover, since the solubility with respect to an organic solvent is low, a solubility margin cannot be obtained. Furthermore, there is a problem of generating an unpleasant odor. In addition, since the organic acid component having a large number of carbon atoms has a small niobium content, a sufficient solubility margin may not be obtained in terms of solubility in terms of mole. In addition, a thin film obtained by using such an organic acid niobium derivative in a precursor has a large amount of impurity carbon residues.

  The method for producing a 2-ethylhexanoic acid niobium derivative of the present invention is a method using pentakis (alkoxy) niobium as a starting material. As a method of using pentakis (alkoxy) niobium as a raw material, a method in which 2-ethylhexanoic acid is added and heated, water generated as a by-product in the reaction between pentakis (alkoxy) niobium and 2-ethylhexanoic acid is removed, and a dehydrating agent is used. The method of using together is mentioned. The reaction ratio of pentakis (alkoxy) niobium and 2-ethylhexanoic acid is in the range of 3 to 8 mol, preferably 4 to 6 mol, of 2-ethylhexanoic acid with respect to 1 mol of pentakis (alkoxy) niobium. . Here, when the amount of 2-ethylhexanoic acid is less than 3 mol, an alkoxy group remains and storage stability is deteriorated, which is not preferable. When it exceeds 8 mol, an effect associated with an increase in the addition amount is exhibited. This is not preferable because it is economically disadvantageous.

  In the method for producing a 2-ethylhexanoic acid niobium derivative of the present invention, examples of pentakis (alkoxy) niobium used as a starting material include pentakis (methoxy) niobium, pentakis (ethoxy) niobium, pentakis (propoxy) niobium, Examples thereof include alkoxides having 1 to 4 carbon atoms such as pentakis (isopropoxy) niobium and pentakis (butoxy) niobium.

  In the case of using pentakis (alkoxy) niobium as a starting material, if water is present in the reaction system, the Nb—O—Nb chain advances, making it difficult to control the reaction. Therefore, it is preferable to use a dehydrating agent that consumes by-produced water as the method for producing the niobium 2-ethylhexanoate derivative of the present invention. Examples of the dehydrating agent include acetic anhydride, maleic anhydride, citraconic anhydride, malonic anhydride, itaconic anhydride, phthalic anhydride, succinic anhydride and the like, and orthoformate such as triethyl orthoformate and trimethyl orthoformate. Examples include esters. Among these, an acid anhydride is preferable because it can be easily removed from the reaction system after the reaction, and acetic anhydride is most preferable. Moreover, the usage-amount of a dehydrating agent is 0.5-10 mol with respect to 1 mol of pentakis (alkoxy) niobium which is a raw material, Preferably it exists in the range of 1-8 mol. If the use amount of the dehydrating agent is less than 0.5 mol, the use effect may not be exhibited, which is not preferable. If the use amount exceeds 10 mol, the effect associated with the increase in the addition amount is not exhibited, which is economical. It is not preferable because it is disadvantageous.

  Moreover, in the manufacturing method of the 2-ethyl hexanoic acid niobium derivative of this invention, reaction temperature is 100-150 degreeC, Preferably it exists in the range of 110-140 degreeC. Here, if the reaction temperature is less than 100 ° C., it takes time to complete the reaction, and an alkoxy group may remain in the product. Is difficult to control, and it may be difficult to control the molecular weight and niobium content.

  When the 2-ethylhexanoic acid niobium derivative of the present invention is used as a raw material for the MOD method, it can be used as a composition containing an organic solvent and a precursor compound or the like that introduces other elements used as needed into the thin film. The form of the composition may be any of emulsion, suspension, dispersion, colloidal dispersion, and solution, but it is used as a solution that can form a thin film with good uniformity of the thin film composition and good surface condition. It is preferable. Further, the content of the niobium 2-ethylhexanoate derivative in the composition is usually in the range of 1 to 50% by mass, preferably in the range of 5 to 40% by mass, which is easy to apply to the substrate. It is.

  Examples of the organic solvent include alcohol solvents, polyol solvents, ketone solvents, ester solvents, ether solvents, polyether solvents, aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, chlorine solvents, cyano solvents. Examples thereof include hydrocarbon solvents having groups, pyrrolidone solvents, and the like, and these can be used alone or in combination.

  As a precursor compound for introducing the other element into the thin film, a metal alkoxide compound, an organic acid metal compound, and a β-diketone metal complex are preferable, and a metal alkoxide compound and an organic acid metal salt compound are more preferable.

Examples of the thin film that can be produced by the MOD method using the MOD raw material using the 2-ethylhexanoic acid niobium derivative of the present invention include dielectrics such as niobium oxide and niobium-tantalum oxide (Ta _2−x Nb _x O ₅ ). Thin film; Piezoelectric thin film such as lithium niobate; Niobium-bismuth tantalate [Bi ₂ (Ta _m Nb _1-m ) ₂ O ₅ ], Niobium-bismuth strontium tantalate (Sr _1-x Ba _x Ta _2-y Nb _y O ₉ ), niobium-doped lead titanate, niobium-doped bismuth titanate, niobium-doped lead titanate, and niobium-doped lead zirconate titanate ferroelectric thin films.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. It should be understood that the present invention is not limited to the following examples.
Example 1 Production of Niobium 2-Ethylhexanoate Derivative 1 Under a dry argon gas atmosphere, 0.5 mol of pentakis (ethoxy) niobium and 200 ml of dry toluene were charged into a reaction flask, and 2.6 mol of acetic anhydride, 2 -After 2.6 mol of ethylhexanoic acid was added and refluxed at a bath temperature of 120 ° C for 4 hours, toluene and low-boiling substances were distilled off from the reaction system at a bath temperature of 135 ° C. To 345 g of a yellow viscous liquid. The resulting yellow viscous liquid was subjected to the following measurements:

(1) Elemental analysis The powder obtained by adding 45% 63% nitric acid water to the sample mass and heating to 100 ° C. was quantified as Nb 2 O 5, and the niobium content was 13.7% by mass.
Moreover, when carbon and hydrogen content were performed by CHN elemental analysis, C content was 55.1 mass% and H content was 8.3 mass%.
(2) Spectral analysis / ¹ H-NMR analysis: The obtained chart is shown in FIG. From the chart of ¹ H-NMR analysis shown in FIG. 1, it was confirmed that the alkoxy group was absent.
* ¹³ C-NMR (solvent: heavy benzene): The obtained chart is shown in FIG. From the chart shown in FIG. 2, it was confirmed that the alkoxy group was absent. A plurality of carbon peaks of 2-ethylhexanoic acid residues were observed. This indicates that there are a plurality of environmental 2-ethylhexanoic acid residues.
IR (coating method): The obtained chart is shown in FIG. From the chart shown in FIG. 3, a plurality of absorptions were observed at 1500 to 1600 cm ^−1, and a plurality of absorptions were also observed at 1400 to 1500 cm ⁻¹ . This indicates that multiple types of COONb exist.
(3) Thermal analysis TG-DTA (air 300 ml / min, temperature rising rate: 10 ° C./min, sample amount 38.8037 mg, reference alumina 7.1320 mg): The obtained chart is shown in FIG.

Comparative Example 1 Production of Niobium 2-ethylhexanoate Derivative 2 Under a dry argon gas atmosphere, 0.5 mol of niobium pentachloride and 200 ml of ethanol were charged into a reaction flask, and 2.6 mol of 2-ethylhexanoic acid was added thereto. The mixture was stirred for 2 hours while blowing gas. The ammonia gas was stopped and refluxed at a bath temperature of 80 ° C. for 4 hours, and then refluxed for another hour while blowing argon gas. The reaction solution was cooled to room temperature, and from the solution from which ammonium chloride was removed by decantation and filtration, the solvent was changed from ethanol to toluene, and the precipitated ammonium chloride was separated by filtration. Toluene and low-boiling substances were distilled off from this solution at a bath temperature of 135 ° C., and the system was further concentrated under reduced pressure to 3 to 1 torr to obtain 345 g of a yellow viscous liquid. Elemental analysis was performed on the obtained yellow viscous liquid in the same manner as in Example 1. As a result, the niobium content was 12.2% by mass and the carbon content was 59.0% by mass.

Comparative Example 2: Production of 2-ethylhexanoic acid niobium derivative 3 Under a dry argon gas atmosphere, 0.5 mol of pentakis (ethoxy) niobium and 200 ml of dry xylene were charged into a reaction flask, and 2.6 ethyl 2-ethylhexanoate was added thereto. After adding 4 moles and refluxing at a bath temperature of 145 ° C. for 4 hours, xylene and low-boiling substances are distilled off from the reaction system at a bath temperature of 145 ° C., and the system is further concentrated under reduced pressure to 3 to 1 Torr. Gave 335 g of a yellow viscous liquid. Elemental analysis was performed on the obtained yellow viscous liquid in the same manner as in Example 1. As a result, the niobium content was 17.4% by mass and the carbon content was 53.0% by mass.

Evaluation 1
The 2-ethylhexanoic acid niobium derivatives 1 to 3 obtained in Example 1, Comparative Example 1 and Comparative Example 2 were evaluated for solubility in organic solvents using toluene and butanol. Table 1 shows the result of mixing 6 g of the organic solvent and 4 g of the 2-ethylhexanoic acid niobium derivative.

Evaluation 2
The 2-ethylhexanoic acid niobium derivatives 1 and 2 obtained in Example 1 and Comparative Example 1 were tested for mixing stability using a pentakis (ethoxy) tantalum 0.6 mol / liter tetrahydrofuran solution. 10 ml of a solution in which 2-ethylhexanoic acid niobium derivative is added to the tantalum alkoxide solution in an amount so that the molar number of niobium is 50% of tantalum and 2-ethylhexanoic acid niobium derivative is not added is placed in a 20 ml sample bottle at 30 ° C. The state of the sample after being stored in a constant temperature and humidity chamber with a humidity of 50% for 18 hours was observed. The results are shown in Table 2.

From the above results, it was confirmed that the niobium 2-ethylhexanoate derivative of the present invention has good solubility in organic solvents and also has good mixing stability with other precursor compounds. It has been confirmed that the tantalum ethoxide has a stabilizing effect. On the other hand, a 2-ethylhexanoic acid niobium derivative having a high niobium content is inferior in solubility, and a 2-ethylhexanoic acid niobium derivative having a low niobium content is inferior in mixing and stabilization with other precursor compounds.
This indicates that the niobium 2-ethylhexanoate derivative of the present invention has a particularly excellent effect as a precursor for the MOD method.

  The niobium 2-ethylhexanoate derivative of the present invention can be suitably used as a precursor for the MOD method.

1 is a chart of ¹ H-NMR analysis of a niobium 2-ethylhexanoate derivative of the present invention obtained in Example 1. 2 is a chart of ¹³ C-NMR analysis of the niobium 2-ethylhexanoate derivative of the present invention obtained in Example 1. FIG. 2 is a chart of IR analysis of the niobium 2-ethylhexanoate derivative of the present invention obtained in Example 1. 2 is a TG-DTA analysis chart of the niobium 2-ethylhexanoate derivative of the present invention obtained in Example 1. FIG.

Claims (6)

  The niobium content is 13 to 16% by mass, the carbon content is in the range of 50 to 58% by mass, and the composition is composed only of niobium atoms, oxygen atoms, and 2-ethylhexanoic acid residues. 2-ethyl hexanoic acid niobium derivative.   The method for producing a 2-ethylhexanoic acid niobium derivative according to claim 1, wherein pentakis (alkoxy) niobium and 2-ethylhexanoic acid are reacted.   The method for producing a 2-ethylhexanoic acid niobium derivative according to claim 2, wherein 4 to 6 mol of 2-ethylhexanoic acid is reacted in the presence of a dehydrating agent with respect to 1 mol of pentakis (alkoxy) niobium.   The manufacturing method of the 2-ethylhexanoic acid niobium derivative of Claim 3 which uses 1-8 mol of dehydrating agents with respect to 1 mol of pentakis (alkoxy) niobium.   The method for producing a 2-ethylhexanoic acid niobium derivative according to claim 3 or 4, wherein 4 to 6 moles of acetic anhydride is used as a dehydrating agent with respect to 1 mole of pentakis (alkoxy) niobium.   The method for producing a niobium 2-ethylhexanoate derivative according to any one of claims 2 to 5, wherein the reaction temperature is in the range of 100 to 150 ° C.

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